This invention relates to supercritical fluid extraction and to assays of natural fats and oils, such as for example, neutral oil and loss determination for soybean and other oilseeds oils.
In supercritical fluid extraction, an extraction vessel is held at a temperature above the critical point and is supplied with fluid at pressure above the critical pressure. Under these conditions, the fluid within the extraction vessel is a supercritical fluid. In one type of apparatus for supercritical extraction, there is a specially constructed extraction vessel within a source of heat.
A prior art apparatus for supercritical extraction of this type is described by B. W. Wright, et al., in ANAL. CHEM. 59 38-44 (January, 1987) using a glass-lined extraction chamber within a bolted stainless steel extraction vessel heated in an oven. This type of extraction apparatus has the disadvantages of: (1) requiring time consuming steps to open the pressurized extraction vessel to insert the sample before use and again to open it after use to remove the spent sample; and (2) under some circumstances requiring the handling of a hot extraction vessel.
It is known how to determine or assay ratios of the components of oilseed oil to characterize the oilseed product. One method of making such an assay or determination is "neutral oil and loss determination."
In the prior art, natural oil and loss determinations are done with non-supercritical fluid extractor methods, such as for example, liquid chromatography, to estimate the amount of refinable oil present in crude oilseed oils. A liquid chromatography method, designated method CA 9f 57, for neutral oil and loss is approved by the American Oil Chemists Society.
In the method approved by the American Oil Chemists Society: (1) the oil is solubilized in an organic solvents; (2) the solubilized oil is passed through a bed of activated alumina separating medium where the polar components of the oil are absorbed; (3) the remaining solution is collected; (4) the neutral oil and loss residue solvents are removed; and (5) the value is determined by mass difference. The apparatus employed in the American Oil Chemists Society method CA 9f 57 is constructed entirely of glass with a gravity-fed solvent.
This current prior art method has several disadvantages such as: (1) large amount of organic solvents are consumed; (2) the method is time consuming; and (3) the alumina bed is prone to plugging.